Looking for articles and or theories that explore the idea that morphology and syntax are not separate but operate on the same principles; for example, that the sentence is just an extended morphological word (using those terms generally, external of their various theoretical use).

[...] we take the phonological realization of the terminal elements in the syntax to be governed by lexical (Vocabulary) entries that relate bundles of morphosyntactic features to bundles of phonological features.

We have called our approach Distributed Morphology to highlight the fact that the machinery of what traditionally has been called morphology is not concentrated in a single component of the grammar, but rather is distributed among several different components.

Two points: first, it is in a sense the opposite of what you mention in your question, in that a morphologically derived word is claimed to have internal syntactic structure. Second, DM is not pure syntax (hence the "Distributed" label): it does have a number of post-syntactic operations that derives morphological generalizations such as syncretism (where different morphosyntactic feature bundles like first person singular and second person singular are realized by the same morpheme).

If one focuses on morphosyntax (inflectional morphology), the differences might be hard to spot. On the other hand, morphological creation of new words (derivational morphology) seems to rely on some different principles. For example:

Idioms are essential to derivational morphology. Existing words change meaning during their existence. The existence of words is so fundamental people argue about it all the time. Sentences usually don't have existence, no one complains about people making up new sentences.

New coinage don't have to be transparent. They can be interpreted through their components and through the context. The sum of information as to reach a certain level to achieve comprehension.

Human language users commit some things about their language to memory, but for other matters, they wing it. The memorized things must be finite in number, of course, because we have only a finite amount of time to memorize and a finite capacity to store memories. But the rest of the language, which we create and understand ad hoc, from expression to expression, is infinite.

We memorize words, but deal with phrases ad hoc, for the most part. The number of words is finite (pace Langendoen and Postal in The Vastness of Natural Languages), while the number of phrases is infinite. Morphology describes words, a finite list of things, but syntax must describe the infinity of phrases, so syntax and morphology must differ in a fundamental way.

The number of actual words, or anything else actual, is finite. The number of morphemes (either way) is also finite. But the number of possible (generable) words is infinite, given any recursive word-formation process. Whether or not we memorize words for the most part would depend on the possibility of having encountered a word like "muvaffakiyetsizleştiricileştiriveremeyebileceklerimizdenmişsinizcesine", or worse.
–
user6726Feb 15 at 21:58